Symfony 3.1 composer conflicts

Question

I'm resuscitating the old Symfony project. Cannot "composer install". I have tried to make changes in packages removing composer.lock , changing versions of packages. Bugs are multiplying. Is there a way to resolve this conflict ?

Problem 1 - symfony/debug is locked to version dev-master and an update of this package was not requested. - Only one of these can be installed: symfony/symfony[v3.1.0], symfony/debug[dev-master]. symfony/symfony replaces symfony/debug and thus cannot coexist with it. - symfony/symfony is locked to version v3.1.0 and an update of this package was not requested.

composer.json :

{
    "name": "symfony/framework-standard-edition",
    "license": "MIT",
    "type": "project",
    "description": "The \"Symfony Standard Edition\" distribution",
    "autoload": {
        "psr-4": { "": "src/" },
        "classmap": [ "app/AppKernel.php", "app/AppCache.php" ]
    },
    "autoload-dev": {
        "psr-4": { "Tests\\": "tests/" }
    },
    "require": {
        "php": ">=5.5.9",
        "symfony/symfony": "3.1",
        "twig/extensions": "^1.4",
        "doctrine/orm": "^2.5",
        "doctrine/doctrine-bundle": "^1.6",
        "doctrine/doctrine-cache-bundle": "^1.2",
        "doctrine/doctrine-migrations-bundle": "^1.2",
        "symfony/swiftmailer-bundle": "^2.3",
        "symfony/monolog-bundle": "^2.8",
        "symfony/polyfill-apcu": "^1.0",
        "symfony/debug": "3.2.x-dev",
        "sensio/distribution-bundle": "^5.0",
        "sensio/framework-extra-bundle": "^3.0.2",
        "incenteev/composer-parameter-handler": "^2.0",
        "liuggio/excelbundle": "^2.1",
        "stof/doctrine-extensions-bundle": "1.2.*@dev",
        "friendsofsymfony/user-bundle": "^2.0",
        "friendsofsymfony/jsrouting-bundle": "^2.0",
        "jms/serializer-bundle": "^1.1",
        "yethee/enum-bundle": "^2.0",
        "webit/eval-math": "^1.0",
        "yavin/symfony-form-tree": "^1.0",
        "knplabs/knp-snappy-bundle": "^1.4",
        "friendsofsymfony/rest-bundle": "^2.1"
    },
    "require-dev": {
        "sensio/generator-bundle": "^3.0",
        "symfony/phpunit-bridge": "^3.0"
    },
    "scripts": {
        "symfony-scripts": [
            "Incenteev\\ParameterHandler\\ScriptHandler::buildParameters",
            "Sensio\\Bundle\\DistributionBundle\\Composer\\ScriptHandler::buildBootstrap",
            "Sensio\\Bundle\\DistributionBundle\\Composer\\ScriptHandler::clearCache",
            "Sensio\\Bundle\\DistributionBundle\\Composer\\ScriptHandler::installAssets",
            "Sensio\\Bundle\\DistributionBundle\\Composer\\ScriptHandler::installRequirementsFile",
            "Sensio\\Bundle\\DistributionBundle\\Composer\\ScriptHandler::prepareDeploymentTarget"
        ],
        "post-install-cmd": [
            "@symfony-scripts"
        ],
        "post-update-cmd": [
            "@symfony-scripts"
        ]
    },
    "config": {
        "bin-dir": "bin",
        "platform": {
            "php": "5.5.9"
        }
    },
    "minimum-stability": "dev",
    "extra": {
        "symfony-app-dir": "app",
        "symfony-bin-dir": "bin",
        "symfony-var-dir": "var",
        "symfony-web-dir": "web",
        "symfony-tests-dir": "tests",
        "symfony-assets-install": "relative",
        "incenteev-parameters": {
            "file": "app/config/parameters.yml"
        },
        "branch-alias": {
            "dev-master": "3.2-dev"
        }
    }
}

Answer 1

I have no idea how this package version got there. I was trying to pick the closest version number from packagist before I have chosen the simplest approach to the problem this time :). I have been downgrading it number by number to 3.1.0 when it finally ran.